Overhead crane girder



Aug. 15, 19 A. v. KORE E TAL OVERHEAD CRANE GIRDER Filed Jan. 22, 1965ATYURiY 2 Sheets-Sheet l g- 15, 1967 A. v. KORE ETAL OVERHEAD CRANEGIRDER 2 Sheets-Sheet 2 Filed Jan. 22, 1965 E D9555 $581128 "3 R 88552502 6 20 F 365K v mm .6 AD. E E Emmi 235d :55 H x8 7 Q a .3 3 8 DJArron/v5) United States Patent 3,335,674 OVERHEAD CRANE GIRDER AlexanderV. Kore, West Allis, and Douglas E. Holt, Mequon, Wis., assignors toHarnischfeger Corporation, West Milwaukee, Wis., a corporation ofWisconsin Fiied Jan. 22, 1965, Ser. No. 427,224 10 Claims. (Cl.105--163) The present invention relates generally to overhead cranes andto an improved girder therefor.

Crane girders of the type to which the present invention relates must becapable of supporting a load which is highly concentrated at onelocation of the girder cross section, and these girders are subjected tothree basic types of loading: vertical, lateral, and torsional.Heretofore, such girders have necessarily been of considerable weightand cross-sectional size in order to safely support the loads imposed onthem. As a result, these girders were not only expensive and required aconsiderable amount of space for their installation, but also requiredthe trolley, which was supported between two of these girders, to be ofconsiderable spread.

In accordance with the present invention, a crane girder has beenprovided which is considerably lighter in weight and smaller in sizethan a conventional prior art girder of comparable stiffness andstrength.

More specifically, the present invention provides a girder of the abovetype in which the section shear center is controlled by proportioningthe section so that the twisting due to asymmetrical bending is kept toa minimum. Preferably, the load application plane passes through theshear center of the girder section.

The invention provides a girder of the above type which is. comprised ofa combination of a beam, of moditied C cross-secti0nel shape, and a boxbeam of rectangular shape in cross section. The result is a girder whichis economical to produce, has adequate lateral stiifness, and has ashear center which is close to the action lines of the load vectors. Theuse of a box beam of relatively small size is possible for providingsufiicient torsional stiffness.

The invention provides a bridge member girder for an overhead cranewhich has section properties that incorporate the light weight of theconventional I or WF beams, combined with the torsional stiffness of aconventional box-type girder. The girder includes a wide top flangewhich assures lateral stiffness to resist loads due to acceleration,deceleration, and side pull which are found in structures utilizing thepresent invention.

The present invention generally provides an improved overhead cranehaving a minimum amount of spread and good economy of design.

These and other objects and advantages of the present invention willappear hereinafter as this disclosure progresses, reference being had tothe accompanying drawings, in which:

FIGURE 1 is a side view of a crane girder made in accordance with thepresent invention;

' FIGURE 2 is a sectional view taken along line 22 in FIGURE 1;

FIGURE 3 is an enlarged sectional view of one of the girders shown inFIGURE 2;

FIGURE 4 is a fragmentary, perspective, exploded view showing theconnection between the girder and end truck;

FIGURES 5 to 9 are schematic, cross-sectional views of various types ofbeams, the beams of FIGURES 5 and 6 being conventional;

FIGURES 10 to 14 are diagrams showing the distribution of normalstresses in the beams of FIGURES 5 to 9, respectively.

3,335,674 Patented Aug. 15, 1967 Referring in greater detail to thedrawings, the crane C in general is mounted on suitable rails 1, 2supported on any suitable overhead structure, indicated partially at 3and 4. The crane includes two girders G which are arranged in spacedapart, parallel relationship and are rigidly secured together at theirends by end trucks 5 and 6. These trucks each have a pair of wheels 7and 8 so that one wheel is located generally at each corner of the craneand which ride on and are guided by the rails 1 and 2. As shown inFIGURES 1, 2, and 3, the ends of the girders are of reduced height, andthe girders and end trucks have abutting surfaces 12 and 13,respectively, which may be rigidly held together in any suitable manneras by welding or by bolt means 14. Drive motors 11 are provided for atleast some of the wheels to furnish the driving power for propelling thecrane along the rails, and if a more complete description of thesemotors is deemed to be either necessary or desirable, reference may behad to our co-pending US. patent application, Ser. No. 426,863, filedJan. 21, 1965, which issued on May 24, 1966 as Patent No. 3,252,586 andentitled Integral and Coaxial Drive Assembly for Crane Wheels.

As shown in FIGURES 1 and 2, a conventional trolley T is mounted on anddriven along the crane C on other rails 15, one located on and rigidlyfixed to the top side of each of the girders G. For this purpose, thetrolley has four wheels 16 and its own power source in the form of theelectric motor 20. A power hoist including a hook 21, cable 22, and itsdrum 23 also forms part of the trolley.

In general, these cranes C may be of considerable length; morespecifically, the girders G may be of considerable length and must becapable of supporting loads of many tons. Accordingly, the strength andthe weight of the girders themselves are of utmost importance.

Crane girders of the above type are subjected to several basic loadingcomponents. For example, they are subjected to vertical loading due tolive loads such as the hook load, trolley weight, and impact. Verticalloading also results from dead loads such as the weight of the girdersthemselves, machinery, and other items. These girders are also subjectedto lateral loading due to acceleration, deceleration, side pull, andswinging loads. In addition, these girders are subjected to torsionalmoments or twisting resulting from an eccentric application of eitherthe vertical or lateral loading, or both.

Referring to FIGURES 5 to 9, the maximum torsional loading results whenthe various torsional components act in the same direction: Maximum M=aL+bV where a and b are the moment arms of the lateral and verticalload vectors L and V, respectively, with respect to the shear center SC.The center of gravity (commonly referred to as the centroid) of thesection has been labeled CG.

In FIGURES 10 to 14, tensile stresses have been indicated with apositive sign, and compressive stresses have been indicated with anegative sign.

FIGURES 5 to 9 represent different types of crane girders. FIGURES 5 and6 represent conventional beams, namely a box beam and an I beam,respectively. FIG- URES 7 and 8 show a C beam and a modified C beam,which are shown and described in order to illustrate the presentinvention, which invention is shown in FIGURE 9 where there is shown abeam made in accordance with the present invention.

Referring more specifically to the girder represented by FIGURES 5 and10, it will be noted that this box section has a very large torsionalstiffness. Disadvantages of this form of girder, however, are poorutilization of material (two web plates are necessary), high dead weightto capacity ratio (especially on short spans), and it requires a largenumber of internal diaphragms because the vertical loading is notapplied at the web plates.

The I girder represented by FIGURES 6 and 11 has relatively goodutilization of material and is therefore of comparatively light weight.It has limited lateral stiffness, however, and poor torsional stiffness.In girders of this type, wing angles or auxiliary trusses are requiredto obtain sufficient stability.

The C beam form of FIGURES 7 and 12 results in good utilization ofmaterial and suflicient lateral stiffness. Because of extremely poortorsional stiffness (note location of shear center), these beams cannotbe used in most cases for main girders.

The modified C beam of FIGURES 8 and 13 has better utilization ofmaterial when compared to the regular C beam type, and the location ofthe shear center is also better. The torsional stiffness, however, isstill insuflicient which precludes this type from being used in generalapplications as a crane girder.

The design shown in FIGURES 9 and 14 is made in accordance with thepresent invention and is a combination of the box and modified Cdesigns. It has been found that this new design results in veryeflicient utilization of material, adequate lateral stiffness, and theshear center is close to the action lines of the load vectors. With thisnew combination design, a small box section is capable of providingsufficient torsional stiffness, and the compressive load can bedistributed over a number of rigid plate elements 26, 26a and 28.Gussets 25 are welded to and within the modified C portion of the girderas shown in FIGURE 3, and these gussets have a reinforcing flange 25::normal thereto and along their inclined outer edge. These gussetsprevent buckling of wall 29 and flange 26.

The new design provides a considerable weight reduction compared to theconventional girder design. The section properties of the new designincorporate the lightness of the conventional I or WF beams combinedwith the torsional stiffness of a conventional box-type girder. The widetop flange 26 assures the necessary lateral stiffness which is essentialin the crane girder design to resist the loads due to acceleration,deceleration, and side pull. Flange 26 has an upturned reinforcingflange 26a along its outer edge. The new design also includes thenarrow, lower flange 27 and a relatively small rectangle or box section28 secured to the vertical wall 29 at the top thereof and adjacent thewide top flange 26. The box 28 is located on the inner side of thegirder (FIGURE 3), and the top flange extends outwardly, with respect tothe trolley. Stated otherwise, the box 28 is located on the side of wall29 which is opposite to the side from which flanges 26 and 27 extend.The rail is located in vertical alignment with the vertical wall 29.

The compressive stress in the vertical wall 29 increases from zero froma point 30 (FIGURE 14) about midway of its height to a maximum stress atthe upper end of the wall.

The location of the new girder section shear center is controlled byproportioning the section in such a manner that the twisting due toasymmetrical bending is kept to a minimum. In the ideal case, the loadapplication plane passes through the shear center of the girder section.

An additional advantage of the new girder is its asymmetrical sectionwith the top flange extending outwardly of the crane in general, whichminimizes the necessary distance between the trolley rails. Thisconsequently results in a crane of minimum spread, as shown in FIGURE 2,thus offering maximum economy in design.

The integral, cross-sectional shape of the new, elongated, steel girdersections of the present invention may be produced by bending, welding,or using extruded sections for the girder component parts, or byutilizing combinations of the above manufacturing methods.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:

1. An elongated, steel overhead crane girder having a transverse andintegral cross-sectional shape comprising: a modified C shape includinga vertical wall, a wide top flange extending from the upper edge of saidwall and to one side thereof, a narrower lower flange extending from thebottom edge of said wall and to said one side thereof; and a relativelysmall rectangle shape at the upper end of said wall and forming acontinuation of said wide top flange and located on the side of saidvertical wall which is opposite to said flanges.

2. A girder as defined in claim 1 further characterized in that saidrectangular shape is formed in part by said vertical wall.

3. A girder as defined in claim 1 further characterized in that saidwall is of a vertical height approximately five times that of the heightof said rectangle shape.

4. An overhead crane comprising a pair of spaced apart girders arrangedin substantial parallelism and rigidly secured together, a rail mountedlongitudinally on each girder and along the top side thereof, said railsadapted to support a load carrying trolley for movement therealong, eachof said girders being fabricated from steel and having a cross-sectionalshape comprising; a modified C shape including a vertical wall, a widetop flange extending from the upper edge of said wall and to one sidethereof, a narrower lower flange extending from the bottom edge of saidwall and to said one side thereof; and a relatively small rectangleshape at the upper end of said wall and forming a continuation of saidwide top flange and located on the side of said vertical wall which isopposite to said flanges; said girders being arranged relative to oneanother with their rectangular shapes positioned inwardly adjacent toone another to thereby minimize the distance between said rails and keepthe trolley width to a minimum.

5. A girder as defined in claim 4 further characterized in that saidrectangular shape is formed in part by said vertical wall.

6. A crane as set forth in claim 4 wherein said vertical wall is of aheight approximately five times that of the height of said rectangularshape.

7. An overhead crane comprising a pair of spaced apart girders arrangedin substantial parallelism, transversely arranged end trucks rigidlysecured between corresponding ends of said girders so as to form a craneof generally rectangular shape when viewed in plan, each of said girdersbeing fabricated from metal and having a crosssectional shapecomprising; a modified C shape including a vertical Wall, a wide topflange extending from the upper edge of said wall and to one sidethereof which is outwardly of said crane, a narrower lower flangeextending from the bottom edge of said wall and to said one sidethereof; and a relatively small rectangle shape at the upper end of saidwall and forming a continuation of said wide top flange and located onthe inner side of said vertical wall which is opposite to said flanges.

8. A crane as set forth in claim 7 wherein said vertical wall is of aheight approximately five times that of the height of said rectangularshape.

9. An overhead crane comprising a pair of spaced apart girders arrangedin substantial parallelism, transversely arranged end trucks rigidlysecured between corresponding ends of said girders so as to form a craneof generally rectangular shape when viewed in plan, a rail mountedlongitudinally on each girder and along the top side thereof, said railsadapted to support a load carrying trolley for movement therealong, eachof said girders being fabricated from metal and having a cross-sectionalshape comprising; a modified C shape including a vertical wail, a widetop flange extending from the upper edge of said Wall and to one sidethereof, a narrower lower flange extending from the bottom edge of saidwall and to said one side thereof; and a relatively small rectangleshape 5 6 at the upper end of said Wall and forming a continuationReferences Cited of said wide top flange and located on the side of saidUNITED STATES PATENTS vertical wall which is opposite to said flanges;said girders 821 13 6 5/1906 Taylor being arranged relative to oneanother with their rectan- 1 541782 6/1925 Baker gular Shaps positionedadjacent to One an h r 5 to thereby minimize the distance between saidTail Sai 2 30 075 3 1953 Omsted 104 125 rails being locatedsubstantially in vertical alignment with 3 094 940 5 19 3 Learmont 1 493 said vertical walls. 3,152,559 10/1964 Harshberger 105-444 10. Acrane as defined in claim 9 further characterized in that said girdershave reduced end portions and said 10 ARTHUR LA POINT PrimaryExaminerend trucks are detachably secured to said portions. H. BELTRAN,Assistant Examiner.

1. AN ELONGATED, STEEL OVERHEAD CRANE GIRDER HAVING A TRANSVERSE ANDINTEGRAL CROSS-SECTIONAL SHAPE COMPRISING: A MODIFIED C SHAPE INCLUDINGA VERTICAL WALL, A WIDE TOP FLANGE EXTENDING FROM THE UPPER EDGE OF SAIDWALL AND TO ONE SIDE THEREOF, A NARROWER LOWER FLANGE EXTENDING FROM THEBOTTOM EDGE OF SAID WALL AND TO SAID ONE SIDE THEREOF; AND A RELATIVELYSMALL RECTANGLE SHAPE AT THE UPPER END OF THE SAID WALL AND FORMING ACONTINUATION OF SAID WIDE TOP FLANGE AND LOCATED ON THE SIDE OF SAIDVERTICAL WALL WHICH IS OPPOSITE TO SAID FLANGES.